UNSETENV(P) POSIX Programmer's Manual UNSETENV(P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEunsetenv - remove an environment variable
SYNOPSIS
#include <stdlib.h>
int unsetenv(const char *name);
DESCRIPTION
The unsetenv() function shall remove an environment variable from the
environment of the calling process. The name argument points to a
string, which is the name of the variable to be removed. The named
argument shall not contain an '=' character. If the named variable does
not exist in the current environment, the environment shall be
unchanged and the function is considered to have completed successâ
fully.
If the application modifies environ or the pointers to which it points,
the behavior of unsetenv() is undefined. The unsetenv() function shall
update the list of pointers to which environ points.
The unsetenv() function need not be reentrant. A function that is not
required to be reentrant is not required to be thread-safe.
RETURN VALUE
Upon successful completion, zero shall be returned. Otherwise, -1 shall
be returned, errno set to indicate the error, and the environment shall
be unchanged.
ERRORS
The unsetenv() function shall fail if:
EINVAL The name argument is a null pointer, points to an empty string,
or points to a string containing an '=' character.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
Refer to the RATIONALE section in setenv() .
FUTURE DIRECTIONS
None.
SEE ALSOgetenv() , setenv() , the Base Definitions volume of
IEEE Std 1003.1-2001, <stdlib.h>, <sys/types.h>, <unistd.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 UNSETENV(P)
